New research suggests humans in industrialized nations are more susceptible to certain diseases and allergies because they aren't exposed enough to micro-organisms, especially early in life.New research suggests humans in industrialized nations are more susceptible to certain diseases and allergies because they aren't exposed enough to micro-organisms, especially early in life. (Charles Rex Arbogast/Associated Press)No matter how much yogurt we eat or kambucha we drink, no matter how much we hear about how bacteria can be beneficial to us, it still can seem creepy that there are up to 1,000 species of bacteria and fungi lounging around on our skin at any given time — 1 trillion or so microscopic residents.

Maybe new research that shows just how one of our many freeloaders pays a little rent will help. It turns out certain species of staphylococcal bacteria help the skin regulate its immune response to injury and ward off disease.

It has long been known that our skin teems with so-called microflora. Earlier research has revealed how many species there are (somewhere between 300 and 1,000), where most thrive best (the forearm) and worst (behind the ear). We know that our good bacteria crowd out pathogenic bacteria and that some even secrete a natural antibiotic to ward off these bad bacteria and secure more space for themselves.


We haven't, though, understood whether or how species work with our bodies to help us. But new research out of the lab of Richard Gallo, professor of medicine and pediatrics and the chief of University of California at San Diego's Division of Dermatology, reveals a tight relationship between staphylococcal bacteria and cells on the outer layer of skin, or epidermis.

The research also offers some biological evidence to support the theory that humans in industrialized nations are more susceptible to certain diseases and allergies because they aren't exposed enough to micro-organisms, especially early in life.

The work, performed by post-doctoral fellow Yu Ping Lai and published in the journal Nature Medicine, shows that skin cells have special receptors that pick up chemical signals from the bacteria that inhibit the cells' inflammatory response to injury.

These cells, called keratinocytes, must receive signals from a receptor called Toll-like receptor 3 in order to generate the normal inflammatory immune response. A chemical produced by the bacteria called staphylococcal lipoteichoic acid prevents the receptor from being activated.

When we wash our hands to remove pathogens, we are also removing bacteria that can help protect us against those same pathogens as well as other diseases. What should we do?

This isn't the case for cells in skin layers below the epidermis, however, so if the cut is deep enough, a more powerful immune response is produced, and we heal.

"Too little inflammation is bad, and too much inflammation is bad," says Gallo.

"What's beautiful about this system is that if the [skin] barrier isn't broken we inhibit inflammation, but if it is broken, we allow inflammation to occur."

Gallo suspects that this system may be upset in patients who suffer from eczema, a disease that involves excessive inflammation. And studies have shown that people with eczema get worse when they move to industrialized nations where, presumably they are exposed to fewer micro-organisms.

This creates a puzzle, though. When we wash our hands to remove pathogens, we are also removing bacteria that can help protect us against those same pathogens as well as other diseases. What should we do?

"Right now, we know absolutely that we need to get rid of the pathogens; hand washing protocols need to be maintained," says Gallo. "The goal would be to develop a hand washing technique that would kill pathogens but leave beneficial bacteria alone."

That would mean developing an anti-bacterial soap that kills only certain bacteria — a tall order. In the meantime, Gallo would like to explore the links between his findings and diseases like eczema and try to understand how other bugs on our skin may help us.

"My suspicion is that we'll find other beneficial roles for other microflora if we keep looking," he says.

So as you curl up in bed tonight, think about the trillion tiny, thriving, vigorous bugs that are nestling with you all over your skin. They're there to help you. Really.